The present invention relates to a method and to a corresponding apparatus for producing a fiber-reinforced plastic component. The plastic component is intended, in particular, for use in a motor vehicle.
The prior art discloses, for example in DE 10 2007 027 755 A1, a method for producing a fiber-reinforced plastic component by use of resin transfer molding. Blow-molded hollow cores which are composed of thermoplastic are used in this method. Fiber material is wrapped around the hollow cores and the hollow cores are filled with water in a subsequent process, in order to be able to withstand the high injection pressure of the inflowing resin.
The object of the present invention is to provide a method for producing a fiber-reinforced plastic component which exhibits process reliability while being carried out in a cost-effective manner and is, therefore, suitable for industrial production. A further goal is to provide a corresponding apparatus for carrying out the method.
This and other objects are achieved by a method for producing a fiber-reinforced plastic component. In particular, the plastic component which is produced in this manner, is used in a motor vehicle. The method includes at least the following acts in the indicated order: (i) providing a blow-molded hollow core, (ii) molding the fiber-reinforced plastic component on the hollow core, (iii) inserting one end of the hollow core between a first roller and a first counter (mating) element, and (iv) drawing the hollow core out of the plastic component by rotationally driving the roller. The counter element is, in particular, in the form of a further roller, so that a pair of rollers is used. The “rotational driving” means that the roller is driven, for example, by use of an electric motor. Therefore, no rotational indirect movement of the roller takes place due to some other movement of the hollow core. Rather, the hollow core is moved by rotationally driving the roller.
Clamping the hollow core by use of pincers and withdrawing the hollow core from the plastic component by use of a winch has also been taken into consideration within the scope of the invention. One disadvantage of this, amongst others, has been found to be that the very long hollow core is withdrawn over a long distance or is wrapped up around the winch. When the end of the hollow core is drawn, the core stretches multiply, wherein local increases in force, in particular at the tapered portion produced, lead to undefined tearing of the hollow core before it is completely withdrawn. Therefore, it has been identified within the scope of the invention that the hollow core has to be withdrawn by the first roller, which can be driven, and the counter element for the purpose of producing appropriate quantities with the appropriate quality. The removed hollow core can be recycled directly downstream of the combination comprising the first roller and a corresponding counter element.
When the hollow core is drawn, it generally stretches. However, a defined method act for stretching the hollow core is preferably provided in order to release the hollow core from the plastic component. In addition to inserting the hollow core between the first roller and the first counter element, at least one further end of the hollow core is inserted into a holding apparatus during said method act. The first roller is rotationally driven and/or the further end is moved by way of the holding apparatus in order to then stretch the hollow core. In this case, the two ends of the hollow core are preferably situated opposite one another. When the hollow core is stretched, it is elongated and therefore detaches from the plastic component. This is carried out, in particular, in the case of very long plastic components.
After the hollow core is stretched, it is preferably provided that the holding apparatus is released again and, therefore, the hollow core can be withdrawn by way of the first roller and the first counter element. However, the hollow core may also tear during stretching. In this case, the hollow core is withdrawn both by way of the first roller and by way of the holding apparatus.
The holding apparatus preferably comprises a second roller and a corresponding second counter (mating) element. The further end of the hollow core is inserted between the second roller and the second counter element. When the hollow core is stretched, it is provided that the first roller and/or also the second roller are rotationally driven.
The first counter element and/or the second counter element are/is preferably in the form of further rollers. These further rollers can be rotationally driven or can be freely rotated. The first roller, together with the first counter element, therefore constitutes a first pair of rollers. The second roller and the second counter element therefore constitute a second pair of rollers.
The hollow core is preferably composed of thermoplastic and can therefore be recycled. To this end, the drawn hollow core is melted and processed to form a new hollow core.
In particular, it is provided that, before the hollow core is melted, at least one of the ends of the hollow core is removed and is not processed to form a new hollow core. The ends of the hollow core are usually contaminated and should therefore not be supplied to the recycling process.
Before the hollow core is melted, the drawn hollow core is preferably comminuted. This comminution preferably takes place directly behind the rollers. The ends are preferably removed before the hollow core is comminuted.
It is advantageously provided that the hollow core is filled with a liquid medium, in particular water, during molding of the plastic component. The liquid medium is drained before the hollow core is drawn.
The hollow core is preferably molded by way of resin transfer molding in a corresponding mold. Before the hollow core is inserted into the mold, corresponding reinforcement fibers, in particular which are composed of carbon and/or glass, are wrapped around or braided with the hollow core. In the mold, plastic, in particular resin, is injected into and onto the reinforcement fibers.
After the fiber-reinforced plastic component is molded, the hollow core, together with the plastic component, is preferably inserted into a corresponding cooling apparatus. The inside dimensions of this cooling apparatus correspond approximately to the mold, so that the cooling apparatus is a mold-like cooling apparatus. The plastic component is fixed within this cooling apparatus, so that the hollow core is preferably also drawn here. However, as an alternative, it is also provided that the plastic component remains in the mold of the resin transfer molding process for the purpose of drawing the hollow core.
It is preferably provided that negative pressure is generated in the hollow core, as a result of which the hollow core can collapse after the resin injection and the curing process in the mold, so that the core can be withdrawn from the component with application of less force. This can be performed in addition to or as an alternative to stretching the hollow core.
The invention further includes an apparatus for carrying out the above-described method. To this end, the apparatus includes a first roller and a corresponding counter element, which is preferably in the form of a further roller. As has been described in the method, the first roller and the first counter element serve to insert the end of the hollow core and to draw the hollow core.
The advantageous refinements described within the scope of the method and dependent claims are accordingly advantageously used in the apparatus according to the invention.
Therefore, it is provided, in particular, that the apparatus according to the invention preferably also includes the holding apparatus. The holding apparatus for its part preferably includes the second roller and the second counter element.
The method described within the scope of the invention for drawing the hollow core by way of the first roller, preferably by way of the first pair of rollers, requires less expenditure on equipment than the prior art.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.